1. Field of the Invention
The present invention relates to a power converting device having a noise filter for a power converter, which filters switching noise occurring with a switching operation of a semiconductor switch element.
2. Description of the Related Art
The switching operation of a semiconductor switch element which configures a power converter such as an inverter, etc. is performed based on a drive signal having a carrier frequency that is on the order of several kHz to ten-odd kHz, for which pulse-width modulation (PWM) is performed. This switching operation causes switching noise of a frequency component that is equal to or higher than several tens kHz from the power converter.
In recent years, a variety of legal regulations have been laid down for such a power converter to suppress the negative effect that a component of 100 kHz or higher exerts on an external device among the frequency components of such switching noise, and a noise filter for a power converter is used to address this problem.
Conventionally, a noise filter for a power converter of such a type is configured by connecting, for example, in the form of an inverted L, a reactor, which is a single unit and is formed by winding an electric wire around a core made of ferrite, an amorphous alloy, a crystal alloy, etc., and a capacitor, which is a single unit and is composed of a film, a chip, etc. A single integrated unit is wired at a stage preceding a power converter, so that switching noise occurring with the switching operation of a semiconductor switch element is filtered.
In recent years, the demand for a power converter in which such a noise filter is mounted has been increasing in order to save space or troublesomeness of wiring the power converter and a noise filter unit.
FIGS. 1 and 2 exemplify a configuration where a noise filter is arranged on a printed circuit board. FIG. 1 is its cross-sectional view, whereas FIG. 2 is its elevation view.
Noise filter elements, such as a reactor L 21, a ground capacitor Cy 22, an interphase capacitor Cx 23, etc. are mounted on a printed circuit board 7 with a pin insertion method, so that a noise filter substrate 8 is configured.
FIG. 3 shows an example where a power converter is configured by incorporating the noise filter substrate 8 shown in FIGS. 1 and 2.
This power converter is divided into upper, middle, and lower stages depending on functions, and is configured by a control substrate 9 that performs a signal process of a CPU, etc. or control operations, etc., a printed circuit board on which the above described noise filter substrate 8 of FIG. 1 is mounted, and a main circuit module 10 in which a rectifying circuit 3 and an inverter circuit 5 composed of a switching element 51 is arranged.
The noise filter substrate 8 is arranged between the control substrate 9 and the main circuit module 10. The control substrate 9 that generates a small amount of heat is normally arranged on the top.
The main circuit module 10 that generates a large amount of heat is directly arranged in the center of a radiating fin 11 via a radiation plate 60 such as a ceramic substrate, a metal base substrate, etc., which has superiority in heat radiation, for ease of cooling. Note that the main circuit module 10 is sealed with a silicon gel 70.
Terminal blocks 43 are arranged on the periphery of the radiating fin 11. The printed circuit board 8 and the control substrate 9 are configured as a plurality of stages via supports 41 fixed to the terminal blocks 43.
The power converter is configured by covering the noise filter substrate 8, the control substrate 9, and the main circuit module 10 with a case 12 fixed to the terminal blocks 43.
Conventionally, however, heat generation is caused by an occurrence loss such as a copper loss, etc. from the reactor 21 that configures the noise filter of this type. As shown in FIG. 3, if the reactor is mounted on the printed circuit board 7 within the power converter, the atmosphere temperature within the case 12 rises. Especially, if the capacity of the power converter increases, the atmosphere temperature within the case 12 significantly rises.
Moreover, since a power converter originally has a large occurrence loss of a power semiconductor, close attention is paid to the cooling of the power converter. A rise in the atmosphere temperature within the case 12, which is caused by another heat source, results in an increase in the temperature of the printed circuit board 7, that is, the control substrate 9, leading to a problem such that the heat-resistant lifetime of the components is shortened.
Additionally, in the 3-stage structure shown in FIG. 3, the heat radiation of the entire power converter deteriorates, and at the same time, its capacity becomes large.
It is desirable that the reactor 21 is arranged to contact the radiating fin 11 as much as possible. This is because cooling effect is low if the reactor 21 is mounted on the printed circuit board 7 within the power converter. However, since a ground potential normally occurs between the reactor 21 and the radiating fin 11, the reactor 21 and the radiating fin 11 must be suitably insulated.
An object of the present invention is to provide a power converting device that can efficiently dissipates heat generated by a noise filter on a radiating fin, and obtain a necessary insulation characteristic.
A power converting device according to the present invention is a power converting device that converts power supplied from a power source, and controls an electric appliance. This device comprises a noise filter unit, a driving unit, a radiation container, and a radiating substrate.
In a first aspect of the present invention, the noise filter unit removes a noise component occurring in the device itself, the driving unit has a function for rectifying the power supplied from the power source via the noise filter unit and a function for controlling the electric appliance, and the radiation container is configured by a substrate on which a thin-film resinous insulation layer and a metal plate are stacked, and has a predetermined thermal conductive characteristic and an insulation characteristic. In the power converting device according to the present invention, the noise filter unit is accommodated within the radiation container by being sealed with a resinous insulation material having a thermal conductive characteristic nearly equal to that of the thin-film resinous insulation layer of the radiation container, and the radiation container accommodating the noise filter unit and the driving unit are directly arranged on the radiating substrate.
In a second aspect of the present invention, the noise filter unit removes a noise component occurring in the device itself, the driving unit has a function for rectifying the power supplied from the power source via the noise filter unit and a function for controlling the electric appliance, and the radiation container is configured by a substrate on which a thin-film resinous insulation layer and a metal plate are stacked, and has a predetermined thermal conductive characteristic and an insulation characteristic. In the power converting device according to the present invention, the noise filter unit is sealed with a first resinous insulation material having a thermal conductive characteristic nearly equal to that of the thin-film resinous insulation layer of the radiation container, the driving unit is sealed with a second resinous insulation material and accommodated with the noise filter unit as one body, within the radiation container. The radiation container accommodating the noise filter unit and the driving unit as one body is directly arranged on the radiating substrate.